The ratio of your monthly allowance to your friend’s monthly allowance is 5 : 3. If you received a monthly allowance of $36, how much did your friend receive?

5/3 = 36/x
Cross multiply:
5x = 36*3
x = 36 • 3 / 5
x = 108/5
x = 21.6

So your friend received $21 and 60 cents

Hope this helps :)

1. use commutative property to reorder the terms.2x+81=0.2. move the constant to right side by adding its opposite on both sides. 2x+81-81=0-81.2x=(-81).3. divide the equation on both sides.2x ÷ 2 = 81 ÷ 2.x = -81/2. your answer is -81/2. if you need to simplify it into a decimal, it’s -40.5.